Field of the Invention
This invention relates to a system for charging containers with solids suspended in a carrier fluid. A particular field of application is the final disposal of contaminated resin used in a nuclear power plant for removing undesirable cations and anions from the reactor coolant or auxiliary systems. The spent resin which is of a granular, sand-like consistency, is temporarily stored in a spent resin tank from which it is transferred into drums that are subsequently sealed and shipped for final disposal.
The transfer of the resin from the spent resin tank to the drums is effected by suspending the resin in a carrier liquid to thus form a slurry which is pumped through a pipeline into the drums. The carrier liquid passes through the drums to ensure that the storage volume of each drum is utilized for the resin itself to the greatest extent possible. When the drum undergoing charging is filled to capacity, an isolation valve controlling slurry flow to that drum is closed and a second isolation valve to an empty drum is opened, whereupon the drum is sealed and removed for final disposition and the resin transfer from the spent resin tank to an empty drum resumes.
For shutting off the isolation valve at the appropriate moment to ensure, on the one hand, that the drum has been filled to capacity and to prevent resin, on the other hand, from backing up into the pipeline from the drum undergoing charging, the resin level in the drum, or at least the desired "full" level thereof has to be reliably determined. Such a resin level determination, however, has for long involved difficulties. A principal source of these difficulties is the desideratum to store resin rather than a water-resin slurry in the drum to more efficiently consume the waste disposal storage volume dedicated to resin. Conventional level instruments, such as floats and differential pressure gauges are unreliable in detecting the actual resin level since the water column within the drum is not typically indicative of the resin volume. A determination of the resin level in the drums indirectly by sensing resin fill data in the spent resin tank has not been readily feasible either, because of similar difficulties in determining or maintaining an inventory of resin volume within the spent resin storage tank.